280 PHILOSOPHICAL TRANSACTIONS. ; [aNNO 1778. 



April Qth, a cold day, with snow, hail, and wind, in the north-east ; at 6 in 

 the evening the ihermoineter in the tree at 45°, the atmosphere at 39°. Here 

 the tree was warmer than the atmosphere, just as might have been expected. If 

 these experiments prove any thing, it is that there is no standard ; and probably 

 these variations arose from some circumstance which had no immediate connec- 

 tion with the internal powers of the tree ; but it may also be supposed to have 

 arisen from a power in the tree to produce or diminish heat, as some of them 

 were in opposition to the atmosphere. 



After having endeavoured to find out the comparative heat between vegetables 

 and the atmosphere, when the vegetables were in action ; I next made my ex- 

 periments on them when they were in the passive life. As the difference was 

 very little when in their most active state, I could expect but very little when the 

 powers of the plant were at rest. From experiment on the more imperfect 

 classes of animals it plainly appears, tiiat though they do not resist the effects of 

 extreme cold till they are brought to the freezing point, they then appear to have 

 the power of resisting it, and of not allowing their cold to be brought much 

 lower. To see how far vegetables are similar to those animals in this respect, I 

 made several experiments : I however suspected them not to be similar, because 

 such animals will die in a cold in which vegetables live ; I therefore supposed that 

 there is some other principle. I did not confine these experiments to the walnut- 

 tree, but made similar ones on several trees of different kinds, as pines, yews, 

 poplars, &c. to see what was the difference in different kinds of trees. The dif- 

 ference proved not to be great, not above a degree or 2 : however, this differ- 

 ence, though small, shows a principle in life, all other things being equal ; for 

 as the same experiments were made on a dead tree, which stood with its roots in 

 the ground, similar to the living ones, they became more conclusive. 



In October I began the experiments upon the walnut-tree, when its powers of 

 action were on the decline, and when it was going into its passive life. 



Exp. 6. October 18th, at half past 6 in the morning, the atmosphere at 

 51°i, the thermometer in the tree wasat55"4; but, on withdrawing and ex- 

 posing it for a few minutes in the common atmosphere, it fell to 50°i. — Exp. 

 7. October 21st, 7 in the morning, the atinospiicre at 41*^, the tree at 47°. — 

 Exp. 8. October 2ist, m the evening at 5 o'clock, the atmosphere at 51°-;, the 

 tree at 57°. — Exp. Q. October 22d, at 7 in the morning, the atmosphere at 42°, 

 the tree at 48°. — Etp. 10. October 22d, 1 o'clock afternoon, the atmosphere 

 at 51", the tree at 53°. — Exp. 11. October 23d, in the evening of a wet day, 

 the atmosphere at 46°, the tree at 48". — Exp. 12. October 28, a dry day, the 

 atmosphere at 45°, the tree at 46°. — Exp. 13. October 29th, a fine day, the 

 atmosphere at 45°, the tree at 49°. — Exp. 14. November 2(1, wind east, the at- 

 mosphere at 43°, tlie tree at 43°. — Exp. 15. November 5th, wet day, the at- 



